Prospective clinical and bacteriological observations in pregnant women and their infants are in progress to assess the role of the group B streptococcus in perinatal morbidity and mortality. Specific epidemiological objectives are (1) to determine the incidence of colonization of the maternal birth canal, (2) to examine factors influencing maternal colonization, (3) to study acquisition of group B streptococci by newborn infants and (4) to evaluate the contribution of these organisms to postpartum infection and to all forms of fetal wastage as well as to the better-known clinical infections of neonatal sepsis and meningitis. Laboratory experiments will explore basic mechanisms of infection and immunity in man and experimental animals. BIBLIOGRAPHIC REFERENCE: Anthony, B. F., Concepcion, N. F.: Group B streptococcus in a general hospital. J. Infect. Dis. 132:561-567, 1975.